Etching composition, etching method, method for manufacturing semiconductor device, and method for manufacturing gate-all-around-type transistor

The present invention relates to etching compositions, an etching method, a method for manufacturing a semiconductor device, and a method for manufacturing a gate-all-around-type transistor.

Integrated circuits are increasingly scaled down according to Moore's law.

In recent years, studies have been conducted to improve performance and advance further scaling-down and integration not only by reducing the size of the conventional planar transistors but also by modifying structures; examples of such modifications include fin-type transistors (fin-type FET) and gate-all-around-type transistors (GAA-type FET).

In fin-type FETs, fins are formed on a silicon substrate in a vertical direction. Accordingly, fin-type FETs have an increased number of transistors per unit area and, in addition, exhibit excellent performance in ON/OFF control at low voltage.

Further improving the performance would require an alteration, such as an increase in an aspect ratio of the fins. However, if the aspect ratio is excessively high, problems arise, such as a collapse of the fins in a cleaning process or a drying process used for the formation of the fins.

In GAA-type FETs, the performance of the transistors per unit area is improved by covering a nanosheet or a nanowire, which serves as a channel, with a gate electrode, thereby increasing an area of contact between the channel and the gate electrode.

The formation of GAA-type FETs requires an etching composition for selectively etching silicon or silicon germanium from a structure in which silicon and silicon germanium are alternately layered.

Patent Literature 1 discloses such an etching composition, which is a composition containing a quaternary ammonium hydroxide compound, specifically, ethyltrimethylammonium hydroxide.

The etching composition disclosed in Patent Literature 1 is one in which the type of the quaternary ammonium hydroxide compound is not optimized, and a chelating agent is not included. For either of these reasons, it cannot be said that the etching composition has sufficient ability to selectively dissolve silicon over silicon germanium.

In the structure disclosed in Patent Literature 1 in which silicon and silicon germanium are alternately layered, the silicon used is polysilicon, which has low crystallinity. It is, therefore, unknown whether a comparable selective dissolution ability can be provided in the case of high-crystallinity silicon, which is used in actual semiconductor devices in many cases.

To date, etching compositions containing various components have been studied as in Patent Literature 1. Unfortunately, it cannot be said that those compositions have had sufficient ability to selectively dissolve silicon over silicon germanium.

An object of the present invention is to provide etching compositions that promote dissolution of silicon while inhibiting dissolution of silicon germanium and, therefore, have an enhanced ability to selectively dissolve silicon over silicon germanium.

Another object of the present invention is to provide an etching method, a method for manufacturing a semiconductor device, and a method for manufacturing a gate-all-around-type transistor; these methods use any of the etching compositions.

The inventors of the present invention found that the later-described etching compositions promote dissolution of silicon while inhibiting dissolution of silicon germanium and, therefore, have an enhanced ability to selectively dissolve silicon over silicon germanium.

Accordingly, the features of the present invention are as follows:

The etching composition of the present invention promotes dissolution of silicon while inhibiting dissolution of silicon germanium and, therefore, has an enhanced ability to selectively dissolve silicon over silicon germanium.

The etching method of the present invention, the method of the present invention for manufacturing a semiconductor device, and the method of the present invention for manufacturing a gate-all-around-type transistor use an etching composition of the present invention. Accordingly, in the etching steps, these methods promote dissolution of silicon while inhibiting dissolution of silicon germanium and, therefore, provide an enhanced ability to selectively dissolve silicon over silicon germanium; consequently, the methods enable high-precision etching to be carried out, thereby enabling high-yield manufacture of desired products.

The present invention will be described in detail below. The present invention is not limited to the embodiments described below and can be practiced with various modifications within the scope of the present invention. In this specification, when numerical ranges are expressed with the term “to”, it should be understood that the preceding and following numerical values or physical property values are inclusive.

An etching composition of the present invention includes a quaternary ammonium salt (A) having 8 or more carbon atoms (hereinafter also referred to as a “component (A)”). Consequently, the etching composition can selectively dissolve silicon over silicon germanium.

In addition, the etching composition of the present invention may include a chelating agent (B) (hereinafter also referred to as a “component (B)”), water (C) (hereinafter also referred to as a “component (C)”), and a water-miscible solvent (D) (hereinafter also referred to as a “component (D)”).

<Component (A)>

The component (A) is a quaternary ammonium salt having 8 or more carbon atoms. The inclusion of a quaternary ammonium salt having 8 or more carbon atoms in the etching composition provides the effect of dissolving silicon or silicon germanium.

The number of carbon atoms of the component (A) may be 8 to 32, which is preferable in terms of providing an enhanced ability to selectively dissolve silicon over silicon germanium. More preferably, the number may be 12 to 24. Examples of the quaternary ammonium salt having 8 or more carbon atoms that serves as the component (A) include quaternary alkyl ammonium salts, such as tetraalkylammonium hydroxides in which one or more of the alkyl groups are optionally substituted, examples of which include tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrahexylammonium hydroxide, tetraoctylammonium hydroxide, and benzyltrimethylammonium hydroxide.

Regarding the quaternary alkyl ammonium salt that serves as the component (A), the four alkyl groups may be identical, which is preferable in terms of providing an enhanced ability to selectively dissolve silicon over silicon germanium; in particular, a quaternary alkyl ammonium salt having four identical alkyl groups may be present preferably in an amount greater than or equal to 50 mass %, more preferably in an amount greater than or equal to 70 mass %, and even more preferably in an amount greater than or equal to 90 mass %, based on the total mass of the component (A), and most preferably, the quaternary alkyl ammonium salt having four identical alkyl groups may be present in an amount of 100 mass %.

The quaternary ammonium salts having 8 or more carbon atoms may be used alone or in a combination of two or more.

Among the quaternary ammonium salts having 8 or more carbon atoms, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, tetrahexylammonium hydroxide, tetraoctylammonium hydroxide, and benzyltrimethylammonium hydroxide are preferable in terms of providing an enhanced ability to selectively dissolve silicon over silicon germanium; tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and benzyltrimethylammonium hydroxide are more preferable; tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide are even more preferable; and tetrabutylammonium hydroxide is most preferable.

A content of the component (A) may be greater than or equal to 1 mass % based on the total mass of the etching composition, which is preferable in terms of providing an enhanced ability to selectively dissolve silicon. More preferably, the content may be greater than or equal to 10 mass %, and even more preferably, greater than or equal to 15 mass %.

The content of the component (A) may be less than or equal to 70 mass % based on the total mass of the etching composition, which is preferable in terms of providing an enhanced ability to selectively dissolve silicon. More preferably, the content may be less than or equal to 55 mass %, and even more preferably, less than or equal to 40 mass %.

Based on the above-mentioned preferred forms of the component (A), an etching composition of the present invention may be an etching composition including the component (A) and in which the component (A) contains at least one compound selected from the group consisting of tetrapropylammonium hydroxide and tetrabutylammonium hydroxide; in the component (A), the content of a quaternary alkyl ammonium salt having four identical alkyl groups is greater than or equal to 50 mass % based on the total mass of the component (A); and the content of the component (A) is greater than or equal to 10 mass % based on the total mass of the composition.

<Component (B)>

The component (B) is a chelating agent. The inclusion of a chelating agent in the etching composition provides the effect of protecting silicon germanium.

Examples of the chelating agent include amine compounds, amino acids, and organic acids. These chelating agents may be used alone or in a combination of two or more. Among these chelating agents, amine compounds, amino acids, and organic acids are preferable in terms of providing an enhanced ability to selectively dissolve silicon over silicon germanium; amine compounds are more preferable.

Examples of the amine compounds include ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, ethylenediamine tetraacetic acid, diethylenetriamine pentaacetic acid, triethylenetetramine hexaacetic acid, diethylenetriaminepentakis(methylphosphonic acid), ethylenediamine-N,N′-bis[2-(2-hydroxyphenyl)acetic acid], N,N′-bis(3-aminopropane) ethylenediamine, N-methyl-1,3-diaminopropane, 2-aminoethanol, N-methyl diethanolamine, and 2-amino-2-methyl-1-propanol. These amine compounds may be used alone or in a combination of two or more.

Among these amine compounds, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, ethylenediamine tetraacetic acid, diethylenetriamine pentaacetic acid, triethylenetetramine hexaacetic acid, diethylenetriaminepentakis(methylphosphonic acid), ethylenediamine-N,N′-bis[2-(2-hydroxyphenyl)acetic acid], N,N′-bis(3-aminopropane) ethylenediamine, N-methyl-1,3-diaminopropane, 2-aminoethanol, N-methyl diethanolamine, and 2-amino-2-methyl-1-propanol are preferable in terms of providing an enhanced ability to selectively dissolve silicon over silicon germanium; ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, ethylenediamine tetraacetic acid, diethylenetriamine pentaacetic acid, triethylenetetramine hexaacetic acid, diethylenetriaminepentakis(methylphosphonic acid), and ethylenediamine-N,N′-bis[2-(2-hydroxyphenyl)acetic acid] are more preferable.

Examples of the amino acids include glycine, arginine, histidine, and (2-dihydroxyethyl)glycine. These amino acids may be used alone or in a combination of two or more.

Among these amino acids, glycine, arginine, histidine, and (2-dihydroxyethyl)glycine are preferable in terms of providing an enhanced ability to selectively dissolve silicon over silicon germanium; (2-dihydroxyethyl)glycine is more preferable.

Examples of the organic acids include oxalic acid, citric acid, tartaric acid, malic acid, and 2-phosphonobutane-1,2,4-tricarboxylic acid. These organic acids may be used alone or in a combination of two or more.

Among these organic acids, oxalic acid, citric acid, tartaric acid, malic acid, and 2-phosphonobutane-1,2,4-tricarboxylic acid are preferable in terms of providing an enhanced ability to selectively dissolve silicon over silicon germanium; citric acid and 2-phosphonobutane-1,2,4-tricarboxylic acid are more preferable.

A content of the component (B) may be greater than or equal to 0.001 mass % based on the total mass of the etching composition, which is preferable in terms of providing an enhanced ability to selectively dissolve silicon over silicon germanium. More preferably, the content may be greater than or equal to 0.005 mass %, and even more preferably, greater than or equal to 0.01 mass %.

The content of the component (B) may be less than or equal to 25 mass % based on the total mass of the etching composition, which is preferable in terms of providing an enhanced ability to selectively dissolve silicon over silicon germanium. More preferably, the content may be less than or equal to 10 mass %, and even more preferably, less than or equal to 6 mass %.

<Component (C)>

It is preferable that the etching composition of the present invention includes water (C) (component (C)), in addition to the component (A) and the component (B).

A content of the component (C) may be greater than or equal to 25 mass % based on the total mass of the etching composition, which is preferable in terms of simplifying the production of the etching composition. More preferably, the content may be greater than or equal to 40 mass %, and even more preferably, greater than or equal to 55 mass %.

The content of the component (C) may be less than or equal to 90 mass % based on the total mass of the etching composition, which is preferable in terms of improving an etching rate. More preferably, the content may be less than or equal to 85 mass %, and even more preferably, less than or equal to 75 mass %.

<Component (D)>

It is preferable that the etching composition of the present invention includes a water-miscible solvent (D) (component (D)), in addition to the component (A) and the component (B). The inclusion of a water-miscible solvent in an etchant provides the effect of protecting silicon germanium.

The water-miscible solvent (D) can be any solvent that is highly soluble in water. Preferably, the water-miscible solvent (D) is a solvent having a solubility parameter (SP value) of greater than or equal to 7.0.

Examples of the water-miscible solvent that serves as the component (D) include polar protic solvents, such as isopropanol, ethylene glycol, propylene glycol, methanol, ethanol, propanol, butanol, glycerol, and 2-(2-aminoethoxy)ethanol; polar aprotic solvents, such as acetone, dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone, and acetonitrile; and nonpolar solvents, such as hexane, benzene, toluene, and diethyl ether. These water-miscible solvents may be used alone or in a combination of two or more. Among these water-miscible solvents, glycerol, 2-(2-aminoethoxy)ethanol, ethylene glycol, and propylene glycol are preferable in terms of providing an enhanced ability to selectively dissolve silicon over silicon germanium.

In instances where the etching composition of the present invention includes the component (D), a content of the component (D) may be greater than or equal to 0.01 mass % based on the total mass of the etching composition, which is preferable in terms of providing an enhanced ability to selectively dissolve silicon over silicon germanium. More preferably, the content may be greater than or equal to 0.1 mass %, and even more preferably, greater than or equal to 1 mass %.

The content of the component (D) may be less than or equal to 30 mass % based on the total mass of the etching composition, which is preferable in terms of providing an enhanced ability to selectively dissolve silicon over silicon germanium. More preferably, the content may be less than or equal to 20 mass %, and even more preferably, less than or equal to 15 mass %.